This invention relates to apertured webs for body exudates absorbent garments such as skin-contactable sheets for disposable diapers and sanitary napkins.
FIG. 8 of the accompanying drawings is a perspective view of a microapertured polymeric web 110 described in Japanese Patent Application Disclosure Gazette (Kokai) No. Sho62-57551 in which the web 110 exhibiting a substantially uniform soft and silky tactile impression. The web 110 is intended to be used as a topsheet or a backsheet in a disposable diaper and made from a relatively thin plastic material as a starting web. Specifically, the starting web is placed on a support such as a mesh wire and transported into a processing zone in which the starting web is subjected to high pressure liquid jets.
The apertured polymeric web 110 is formed on its skin-contactable surface with a plurality of cylindrical projections 120 which have, in turn, microapertures 125 at their tops. Each of these microapertures 125 is formed along its peripheral edge with irregularly shaped petals. The web 110 is claimed to have a soft fabric-like touch and to present no surface gloss.
Whether the polymeric web used in disposable diapers or sanitary napkins present a soft touch or not when such web is in contact with the wearer""s skin is often determined on the basis of a certain softness reference, for example, softness of a woven or nonwoven fabric made of natural fibers or synthetic fibers.
In the polymeric web, a peripheral edge of each microaperture formed at the top of each cylindrical projection is finely divided so as to form the irregularly shaped petals. Probably the irregularly shaped petals provide a soft fabric touch when the wearer""s skin rubs the irregularly shaped petals. However, even when the polymeric web is formed with a plurality of the cylindrical projections, there is an apprehension that these projections may rather increase a rigidity of the web. Accordingly, it is difficult for the polymeric web to reconcile a high softness and a high drapeability as provided by a woven- or nonwoven fabric. A topsheet in a body exudates absorbent garment can comfortably adopt itself to the wearer""s skin only when the softness and drapeability are well reconciled.
A drapeability of the polymeric web can be improved by thinning the polymeric web. For example, use of low density polyethylene having a thickness of 0.001xcx9c0.020 mm as the topsheet in disposable diapers or sanitary napkins will be effective to improve the drapeability. However, such excessively thin web will inevitably confront problems such that the web must be handled with excessive carefulness during the process for manufacturing diapers or napkins and the web can not be easily peeled off from the wearer""s skin once the web has been electrostatically attracted on the wearer""s skin.
In view of the above problems, the invention first aims to improve a drapeability of the conventional polymeric web having a soft fabric-like touch. The invention further aims to facilitate the relatively thin polymeric web having its drapeability improved to be handled during the process of manufacturing disposable garments. The invention additionally aims to provide a method for manufacturing the polymeric web having a softness as well as a high drapeability and having its handling facilitated.
According to first and second aspects of the invention, respectively, as will be described below:
The first aspect of the invention relates to an apertured web for a disposable garment, the apertured web comprising: an apertured polymeric web having upper and lower surfaces, the apertured polymeric web being 0.001xcx9c0.05 mm and including a plurality of substantially flat portions, each being 0.03xcx9c1 mm wide, extending in parallel one to another in one direction and a plurality of intermittent apertures extending in the one direction between each pair of the flat portions so as to form a plurality of aperture rows extending in parallel one to another in the one direction; the flat portions adjacent one to another with the aperture rows therebetween being interconnected by a plurality of bridge-like portions extending both of the flat portions adjacent one to another across the aperture rows; and the intermittent apertured being defined by edges of the flat portions extending in the one direction and edges of the bridge-like portions extending transversely of the flat portions, the flat portions being formed at least along the edges thereof extending in the one direction with a plurality of substantially saw-tooth-shaped rising portions rising upward from the upper surface of the flat portions so as to make the upper surface more rough than the lower surface of the flat portions.
The first aspect of the invention includes preferable embodiments as follows:
(1) Most of the intermittent apertures have a width of 0.07xcx9c1 mm and a length corresponding to 1.5 or more times of the width.
(2) A tension exerted on the web transversely of the aperture rows causes only the bridge-like portions to be stretched and thereby causes the web to be stretched transversely of the aperture rows.
(3) A fibrous layer having a basis weight of 2xcx9c30 g/m2 is joined to the lower surface of the polymeric web to form a composite web.
(4) The fibrous layer comprises thermoplastic synthetic fibers or chemical fibers having a fineness of 1xcx9c15 d.
(5) The fibrous layer includes natural fibers.
(6) The fibrous layer comprises hydrophilic fibers.
(7) The polymeric web is formed with a plurality of liquid guiding passages each having a diameter of 0.1xcx9c5 mm and extending downward from the upper surface.
The second aspect of the invention relates to a method for continuously manufacturing an apertured web composed of an apertured polymeric web as first web having upper and lower surfaces, sheet-like fibrous assembly as a second web having upper and lower surfaces, the upper surface of the second web being joined to the lower surface of the first web, and a plurality of rising portions formed on the upper surface of the first web by a part of the first web so as to make the upper surface of the first web rough, the method comprising the steps of:
a. continuously feeding the first web in one direction;
b. continuously feeding the second web in the one direction so that the upper surface of the second web is placed upon the lower surface of the first web, followed by joining these first and second webs together under a pressure to form a first composite web;
c. continuously feeding the first composite web in one direction so that the upper surface of the first web as one component of the first composite web is subjected to pillar-shaped water jets supplied from nozzle means having a plurality of fine orifices arranged transversely of the one direction and, if desired, the upper surface of the first web is repeatedly subjected to the pillar-shaped water jets describing their corresponding loci substantially aligned one with another until the first web is at least locally torn along the loci, thereby the first web is formed with a plurality of aperture rows extending in parallel one to another in the one direction and second composite web is obtained; and
d. continuously feeding the second composite web in one direction so that the lower surface of the second web as the other component of the second composite web is subjected to pillar-shaped water jets supplied from nozzle means having a plurality of fine orifices arranged transversely of the one direction, using pillar-shaped water jets preferably arranged so as to describe their loci substantially aligned with the loci described by the corresponding pillar-shaped water jets on the step c, more preferably two or more times, until the first web is partially deformed substantially in the saw-tooth-shape upward from the lower surface of the first web along peripheral edges of the apertures in the respective aperture rows which have been formed as a result of local tearing of the first web under the effect of the pillar-shaped water jets.
The second aspect of the invention includes preferable manners of execution as follows:
(1) The step b comprises a step of pressing the first web in its thermally softened state against the second web.
(2) The step b comprises a step of feeding the first web together with a second web into a nip between a pair of heated rolls to heat-seal these two webs.
(3) The step b comprises a step of bonding the first and second webs together by means of adhesive agent.
(4) The first web includes any one of the thermoplastic synthetic fibers, chemical fibers and natural fibers.
(5) The method further including a step of making the second web hydrophilic.